Increase priority of raster threads on Android.

base/threading/platform_thread_android.cc

Index: base/threading/platform_thread_android.cc
diff --git a/base/threading/platform_thread_android.cc b/base/threading/platform_thread_android.cc
index 11e5e2e3c870d25d79d205e7dcd349239a02eac2..e661af5eab0c96d7d73f72e670e90ef15d8f4663 100644
--- a/base/threading/platform_thread_android.cc
+++ b/base/threading/platform_thread_android.cc
@@ -23,22 +23,15 @@ namespace base {
 
 namespace internal {
 
-// These nice values are taken from Android, which uses nice values like linux,
-// but defines some preset nice values.
-//   Process.THREAD_PRIORITY_AUDIO = -16
-//   Process.THREAD_PRIORITY_BACKGROUND = 10
-//   Process.THREAD_PRIORITY_DEFAULT = 0;
-//   Process.THREAD_PRIORITY_DISPLAY = -4;
-//   Process.THREAD_PRIORITY_FOREGROUND = -2;
-//   Process.THREAD_PRIORITY_LESS_FAVORABLE = 1;
-//   Process.THREAD_PRIORITY_LOWEST = 19;
-//   Process.THREAD_PRIORITY_MORE_FAVORABLE = -1;
-//   Process.THREAD_PRIORITY_URGENT_AUDIO = -19;
-//   Process.THREAD_PRIORITY_URGENT_DISPLAY = -8;
-// We use -6 for display, but we may want to split this into urgent (-8) and
-// non-urgent (-4).
+// - BACKGROUND is 9 due to it being the nicest value we can use that's still

[danakj, 2015/07/06 23:24:22]

Thanks this comment is awesome.

+// above an Android system threshold that enables heavy throttling starting at
+// 10; we want to be lower-priority than Chrome's other threads without
+// incurring this behavior.
+// - DISPLAY is -6 due to being midway between Android's DISPLAY (-4) and
+// URGENT_DISPLAY (-8).
+// - REALTIME_AUDIO corresponds to Android's THREAD_PRIORITY_AUDIO = -16 value.
 const ThreadPriorityToNiceValuePair kThreadPriorityToNiceValueMap[4] = {
-    {ThreadPriority::BACKGROUND, 10},
+    {ThreadPriority::BACKGROUND, 9},
     {ThreadPriority::NORMAL, 0},
     {ThreadPriority::DISPLAY, -6},
     {ThreadPriority::REALTIME_AUDIO, -16},